What's So Special About Relativity?

Einstein's first theory of relativity, which he published in 1905, broke away from the Newtonian reliance on space and time as immutable frames of reference. This theory was immediately recognized by the scientific community as having profound implications for physics and cosmology.

Einstein's main goal was to address the apparent inconsistencies in Maxwell's electromagnetic theory. No wonder Einstein named his paper The Electrodynamics of Moving Bodies.

Einstein's 1905 paperon Special Relativity
Later to become known as the Special Theory of Relativity, its first postulate was that the speed of light is the same for all observers, regardless of their motion relative to the source of the light. The second postulate was that all observers moving at constant speed should observe the same physical laws. Putting these two ideas together, Einstein showed that the only way this can happen is if time intervals and/or lengths change according to the speed of the system relative to the observer's frame of reference. This flies against our everyday experience but has since been demonstrated to hold in a number of very solid experiments. For example, scientists have shown that an atomic clock travelling at high speed in a jet plane ticks more slowly than its stationary counterpart.

Einstein's discovery of the relativity of space and time led to an equally revolutionary insight. Matter and energy are interrelated, even equivalent. The equivalence of matter and energy is summed up in the famous equation:

Where m = mass and c = the speed of light.

Einstein's 1905 theory is referred to as the "special" theory because it is limited to bodies moving in the absence of a gravitational field. It took Einstein eleven more years to formulate a set of general laws that took account of gravity. The result: Einstein's second landmark paper on General Relativity.